Elucidating the Conductivity-Type Transition Mechanism of p-Type Cu[sub 2]O Films from Electrodeposition

Narrow bandgap films of p- and n-type conductivities are electrodeposited on conducting glass substrates from aqueous solutions. These films exhibit photoelectrochemical responses under visible light illumination. The p- and n-type films have different preferred out-of-plane orientations of [111] and [100], respectively. X-ray absorption fine structure spectroscopic analysis shows that the n-type contains a higher degree of lattice disorder. Ultraviolet photoelectron spectroscopy along with the Mott–Schottky electrochemical impedance analysis determines the energy-level diagrams of both the p- and n-type films. On the basis of the structural features obtained, this paper finds that strong absorption on the unstable surface states resulting from the Cu vacancies of can lead to the formation of an inversion layer and thus conductivity transition from p to n type. As a consequence of this p–n transition mechanism, films containing nanocavities for strong absorption exhibit an n-type conductivity, while intact films are p type. A conductivity-type diagram is constructed to show that a subtle change in the deposition parameters can tune the crystal orientation and conductivity type of films.